The control switch box of a regular ceiling fan, as shown in FIG. 1, is generally comprised of a casing covered by a bottom cover, a pull switch received inside the casing and having a hollow screw rod extended out of a wire hole on the casing and fixed in place by a screw nut permitting the pull wire of the pull switch to be guided out of the casing and the screw nut through the wire hole, and a forward/backward switch fastened to the inside wall of the casing by screws and having a switching lever extended out of an opening on the casing for controlling the revolving direction of the fan motor. This structure of a ceiling fan control switch box is functional however, it is not suitable for use outdoors because rain water may enter the casing through the wire hole or the opening on the casing, causing damage to the electric circuit.